Gastroenteritis in children
Gastroenteritis is an infection that causes vomiting and diarrhea.
Gastroenteritis can be due to an infection with a virus, bacteria, or parasites. Also called the "stomach flu," it is contagious and spreads easily in childcare and schools. It often also causes fever.
Stool samples might be tested for bacteria or parasites if there is blood in the stool. Antibiotics are usually not needed except for certain types of infections in young infants and in people with immune problems.
Gastroenteritis usually is not serious and generally lasts a few days. The greatest risk from gastroenteritis is dehydration, so it's most important to stay hydrated with plenty of fluids. Young kids are at the highest risk for dehydration.
Source: http://kidshealth.org/parent/dictionary/g/az-gastroenteritis.html